OPINION — “The need for accurate and uninterrupted PNT (Positioning, Navigation and Timing) has never been more essential to our warfighters who operate in GPS (Global Positioning System)-denied environments. The successful launch of the NTS-3 (Navigation Technology Satellite-3) system is the first step in updating 20th century technology to help address current threats to our national security.”
That was Ed Zoiss, President of the Space & Airborne Systems segment for L3Harris Technologies, speaking August 13, about the successful launch and arrival in orbit of NTS-3, the most advanced U.S. experimental navigation satellite in nearly 50 years, that was designed and led by the Air Force Research Laboratory (AFRL) with L3Harris Technologies as prime contractor.
NTS-3 is managed by the AFRL Transformational Capabilities Office in partnership with the U.S. Space Force and U.S. Air Force.
Space Force’s GPS provides critical positioning capabilities to military, civilian, and commercial users around the world. The United States government created GPS for the military in 1973, launched the first satellite in 1978, made the system available to civilians in 1988, and has operated the full system of 24 satellites since 1993.
Today it is freely accessible to anyone with a GPS receiver, which means more than six billion users worldwide, according to GPS World, with an estimated 170 million in the U.S. Every day, GPS satellites aid in air traffic control, banking, farming, cellular networks, and countless other industries, and it is perhaps the space system that most people around the world depend on each day.
However, according to the Air Force, “The rapidly increasing pace of new threats to GPS, such as jamming and spoofing, indicate that agile and resilient approaches to augment the GPS system are needed to maintain users’ access to its critical service.”
The GPS system’s 24 operational satellites are strategically placed in six medium earth orbits (MEOs), at an altitude of approximately 12,550 miles, with three to four satellites in each plane making two orbits a day. This configuration ensures that at least six satellites are visible from any point on Earth at any given time.
NTS-3, is expected to change the architecture for satellite navigation and to deliver more robust PNT capabilities to warfighters.
NTS-3 will carry out some 100 tests over the coming year from near-geosynchronous orbit (GEO), where the satellite orbits directly above the equator at about 22,236 miles above the earth. The satellite's orbital period is close to 24 hours and appears stationary from the ground,
thus giving NTS-3 a clear, unobstructed and distinct vantage point without the interruption of weather or atmospheric distortion.
The NTS-3 program integrates a space-based payload, a reconfigurable ground control segment, and agile user receivers -- all linked by reprogrammable software. This architecture allows for rapid updates across all segments, enabling operators to counter jamming, deploy new signals, and adapt to evolving mission requirements without replacing hardware.
According to an AFRL release, “The [NTS-3] satellite will broadcast navigation signals from its phased-array antenna, which can electronically steer signals to a desired region [on earth] without physically moving the satellite. These signals are created through a digital, on-orbit reprogrammable PNT signal generator, which not only supports legacy signals and advanced signals not currently broadcast on GPS, but also allows new signal updates after launch.”
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NTS-3 will test a new digital signal generator, AFRL said, “that can be reprogrammed on-orbit, enabling it to broadcast new signals, improve performance by avoiding and defeating interference, and adding signatures to counter spoofing.” A goal is to make possible the uploading of a signal to the satellite and start transmitting it without having to relaunch the entire satellite.
AFRL also said NTS-3 will also test “the CHIMERA (Chips-Message Robust Authentication) signal authentication protocol, which is designed to jointly authenticate satellite orbit data and measurements of the range between the satellite and user.” CHIMERA provides “an extremely robust protection against GPS spoofing for civil users. Future versions of CHIMERA, or different kinds of signals, can be uploaded to the satellite at any point after launch, based on new knowledge or threat developments on the ground.”
Over the next year, AFRL will conduct a series of demonstrations to assess these technologies in realistic operational scenarios, from countering electronic interference to rapidly deploying new signal configurations in response to emerging threats.
“Because SATNAV (satellite navigation) is critically dependent on precise timekeeping,” AFRL said, “NTS-3 will have multiple atomic clocks and timing sources onboard the satellite that will be used both independently and as an optimized ensemble to allow for automatic clock error detection and correction.”
The NTS-3 Ground Control Segment (GCS), AFRL said, is compatible with the Enterprise Ground Services, an architecture that the Space Forces’ Space and Missile Systems Center is developing, to provide a common system for satellite command and control. “The goal is to move from a portfolio of stove-piped ground systems to a single system that will connect with all Air Force and Space Force satellites, saving millions of dollars by streamlining user training and operations,” AFRL said.
NTS-3 ground control is also planning to leverage commercially-available services such as ground antennas and monitoring receivers to increase opportunities for contact time with the satellite while reducing dependence on already strained government antenna resources.
AFRL is also working with the non-profit MITRE Corp., to develop a reprogrammable software-defined receiver called the Global Navigation Satellite System Test Architecture (GNSSTA). That new receiver will allow users to receive both legacy GPS and advanced signals generated by NTS-3 -- and is of course critical.
Warfighters will be the ultimate beneficiaries of the impact of new navigation technologies and integrated SATNAV capabilities, and any changes to the signal being broadcast from space must be communicated to and coordinated with that user segment. NTS-3 tests will be used to demonstrate new features for warfighters carrying so-called Software-Defined Radios (SDRs), capable of receiving and processing reprogrammable SATNAV signals.
Testing will show whether warfighter SDRs “will be able to access accurate PNT data and enhanced flexible anti-jam and anti-spoof protections,” according to AFRL. “Lessons from the GNSSTA software architecture developed through NTS-3 will pave the way for future DoD major defense programs to successfully connect service men and women to a flexible and resilient SATNAV architecture of the future.”
Much like downloading a new smartphone app, think of what future NTS-3 software updates can bring routinely to future users without the recapitalization effort typically required to upgrade.
This is the future for users of GPS. Hopes are high that NTS-3 will guide us down the right path.
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